llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT--> @llvm/pr-subscribers-lldb Author: Michael Buch (Michael137) <details> <summary>Changes</summary> To get the number of children for a VectorType (i.e., a type declared with a `vector_size`/`ext_vector_type` attribute) LLDB previously did following calculation: 1. Get byte-size of the vector container from Clang (`getTypeInfo`). 2. Get byte-size of the element type we want to interpret the array as. (e.g., sometimes we want to interpret an `unsigned char vec[16]` as a `float32[]`). 3. `numChildren = containerSize / reinterpretedElementSize` However, for step 1, clang will return us the *aligned* container byte-size. So for a type such as `float __attribute__((ext_vector_type(3)))` (which is an array of 3 4-byte floats), clang will round up the bit-width of the array to `16`. (see [here](https://github.com/llvm/llvm-project/blob/ab6a66dbec61654d0962f6abf6d6c5b776937584/clang/lib/AST/ASTContext.cpp#L1987-L1992)) This means that for vectors where the size isn't a power-of-2, LLDB will miscalculate the number of elements. **Solution** This patch changes step 1 such that we calculate the container size as `numElementsInSource * byteSizeOfElement`. This mimicks the typical `sizeof(array) / sizeof(array[0])` calculation in C. --- Full diff: https://github.com/llvm/llvm-project/pull/68907.diff 3 Files Affected: - (modified) lldb/source/DataFormatters/VectorType.cpp (+47-17) - (modified) lldb/test/API/functionalities/data-formatter/vector-types/TestVectorTypesFormatting.py (+7) - (modified) lldb/test/API/functionalities/data-formatter/vector-types/main.cpp (+3-1) ``````````diff diff --git a/lldb/source/DataFormatters/VectorType.cpp b/lldb/source/DataFormatters/VectorType.cpp index 4afcfa2e8e490e0..93eea9507242a9a 100644 --- a/lldb/source/DataFormatters/VectorType.cpp +++ b/lldb/source/DataFormatters/VectorType.cpp @@ -169,21 +169,49 @@ static lldb::Format GetItemFormatForFormat(lldb::Format format, } } -static size_t CalculateNumChildren( - CompilerType container_type, CompilerType element_type, - lldb_private::ExecutionContextScope *exe_scope = - nullptr // does not matter here because all we trade in are basic types - ) { - std::optional<uint64_t> container_size = - container_type.GetByteSize(exe_scope); - std::optional<uint64_t> element_size = element_type.GetByteSize(exe_scope); - - if (container_size && element_size && *element_size) { - if (*container_size % *element_size) - return 0; - return *container_size / *element_size; - } - return 0; +/// \brief Returns the number of elements stored in a container +/// (with element type 'container_elem_type') as if it had elements +/// of type 'element_type'. +/// +/// For example, a container of type +/// `uint8_t __attribute__((vector_size(16)))` has 16 elements. +/// But calling `CalculateNumChildren` with an 'element_type' +/// of `float` (4-bytes) will return `4` because we are interpreting +/// the byte-array as a `float32[]`. +/// +/// \param[in] container_elem_type The type of the elements stored +/// in the container we are calculating the children of. +/// +/// \param[in] num_elements Number of 'container_elem_type's our +/// container stores. +/// +/// \param[in] element_type The type of elements we interpret +/// container_type to contain for the purposes of calculating +/// the number of children. +/// +/// If size of the container is not a multiple of 'element_type' +/// returns 0. +/// +/// On error, returns 0. +static size_t CalculateNumChildren(CompilerType container_elem_type, + uint64_t num_elements, + CompilerType element_type) { + std::optional<uint64_t> container_elem_size = + container_elem_type.GetByteSize(/* exe_scope */ nullptr); + if (!container_elem_size) + return 0; + + auto container_size = *container_elem_size * num_elements; + + std::optional<uint64_t> element_size = + element_type.GetByteSize(/* exe_scope */ nullptr); + if (!element_size || !*element_size) + return 0; + + if (container_size % *element_size) + return 0; + + return container_size / *element_size; } namespace lldb_private { @@ -221,11 +249,13 @@ class VectorTypeSyntheticFrontEnd : public SyntheticChildrenFrontEnd { m_parent_format = m_backend.GetFormat(); CompilerType parent_type(m_backend.GetCompilerType()); CompilerType element_type; - parent_type.IsVectorType(&element_type); + uint64_t num_elements; + parent_type.IsVectorType(&element_type, &num_elements); m_child_type = ::GetCompilerTypeForFormat( m_parent_format, element_type, parent_type.GetTypeSystem().GetSharedPointer()); - m_num_children = ::CalculateNumChildren(parent_type, m_child_type); + m_num_children = + ::CalculateNumChildren(element_type, num_elements, m_child_type); m_item_format = GetItemFormatForFormat(m_parent_format, m_child_type); return false; } diff --git a/lldb/test/API/functionalities/data-formatter/vector-types/TestVectorTypesFormatting.py b/lldb/test/API/functionalities/data-formatter/vector-types/TestVectorTypesFormatting.py index 4103d62878c70f3..1839c28aeb29fc6 100644 --- a/lldb/test/API/functionalities/data-formatter/vector-types/TestVectorTypesFormatting.py +++ b/lldb/test/API/functionalities/data-formatter/vector-types/TestVectorTypesFormatting.py @@ -86,3 +86,10 @@ def cleanup(): v.SetFormat(lldb.eFormatVectorOfFloat32) oldValueAgain = v.GetChildAtIndex(0).GetValue() self.assertEqual(oldValue, oldValueAgain, "same format but different values") + + # Test formatter for vector types whose size is not a power-of-2 + f3 = self.frame().FindVariable("f3") + self.assertEqual(f3.GetNumChildren(), 3) + self.assertEqual(f3.GetChildAtIndex(0).GetData().float[0], 1.25) + self.assertEqual(f3.GetChildAtIndex(1).GetData().float[0], 2.50) + self.assertEqual(f3.GetChildAtIndex(2).GetData().float[0], 2.50) diff --git a/lldb/test/API/functionalities/data-formatter/vector-types/main.cpp b/lldb/test/API/functionalities/data-formatter/vector-types/main.cpp index ef0a227560bc253..7f2309e776bc27e 100644 --- a/lldb/test/API/functionalities/data-formatter/vector-types/main.cpp +++ b/lldb/test/API/functionalities/data-formatter/vector-types/main.cpp @@ -1,8 +1,10 @@ typedef float float4 __attribute__((ext_vector_type(4))); -typedef unsigned char vec __attribute__((ext_vector_type(16))); +typedef unsigned char vec __attribute__((ext_vector_type(16))); +typedef float float3 __attribute__((ext_vector_type(3))); int main() { float4 f4 = {1.25, 1.25, 2.50, 2.50}; vec v = (vec)f4; + float3 f3 = f4.gba; return 0; // break here } `````````` </details> https://github.com/llvm/llvm-project/pull/68907 _______________________________________________ lldb-commits mailing list lldb-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
